Scanning device and method for saving compensation memory

ABSTRACT

A method of reducing memory requirement in the compensation memory unit of a scanner. The method includes providing an even compensation data value and an odd compensation data value and averaging the two to produce an odd-even compensation data value. Only half as much memory space is required to hold the averaged odd-even compensation data values.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Patent Application of U.S. patent applicationSer. No. 09/925,002, filed Aug. 8, 2001 issued as U.S. Pat. No.7,206,093, which claims the benefit of foreign priority under 35 USC§119(a) to Taiwan, R.O.C. Application Ser. No. 90113920, filed Jun. 8,2001.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a scanning device and a scanningmethod. More particularly, the present invention relates to a scanningdevice and a scanning method capable of saving some compensation memory.

2. Description of Related Art

Due to rapid development of multi-media systems, there is a demand forimages with a higher resolution. To increase image resolution, thenumber of light-sensitive cells (such as charge coupled device (CCD)) inthe sensing device of a scanner must increase correspondingly.

Because of some intrinsic properties of a charge-coupled device (CCD) ormanufacturing deviation, sensitivity of each CCD cell may not beidentical. Hence, before scanning an object, the scanner must perform alight-intensity calibration to produce a set of shading values so thatimage compensation can be conducted subsequently. Any non-uniformlight-intensity effects in the pixels generated by the CCD can becompensated for using the shading values. Ultimately, color of the pixeland the color on the target object are identical. To use the shadingvalues in image compensation, the shading values need to be stored incompensation RAM units inside the scanning device. As resolution of ascanner increases, the number of pixels in a CCD increasescorrespondingly. Since a larger compensation memory must be used tostore up the shading values required to compensate the light-intensityof a scanned image, production cost of a scanner increases.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a deviceand a method of saving compensation memory for holding shading values ina scanner. The shading values are divided into odd shading values andeven shading values. The odd and the even shading values are averaged toproduce an odd-even shading value. Two consecutive sets of image pixelsobtained through a charge-coupled device (CCD) use the same odd-evenshading values for image compensation. With this arrangement, only halfof the conventional compensation memory in a scanner is required.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, theinvention provides a compenstation memory saving scanning device. Thedevice includes an input device, an application-specific integratedcircuit, a compensation memory unit, an image memory unit and aninput/output interface. The application-specific integrated circuitcouples with the input device, the compensation memory unit, the imagememory unit and the input/output interface.

Even data values and odd data values are input to theapplication-specific integrated circuit via the input device. Afterperforming a computation using the even data values, the odd data valuesand preset values, the application-specific integrated circuit averagesout the even compensation values and the odd compensation values toproduce averaged odd-even compensation values. The averaged odd-evencompensation values are stored inside the compensation memory unit.Scanned pixel data are stored inside the image memory unit beforeoutputting to the input/output interface.

This invention also provides a scanning method capable of saving somecompensation memory. First, even compensation values necessary forcompensating even-numbered pixels and odd compensation values necessaryfor compensating odd-numbered pixels are extracted. The evencompensation values and the odd compensation values are averaged toproduce averaged odd-even compensation values.

Compensation values necessary for compensating an image must be storedinside a compensation memory unit. To save some compensation memoryspace, odd compensation values and even compensation values are averagedto produce half as much even-odd compensation values so that only halfof the memory is required to hold the data.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

FIG. 1 is a block diagram showing a scanning device capable of savingcompensation memory according to one preferred embodiment of thisinvention;

FIG. 2 is a schematic diagram of an alternative-sensing device forholding compensation data according to one preferred embodiment of thisinvention;

FIG. 3 is a schematic diagram of a linear-sensing device for holdingcompensation data according to one preferred embodiment of thisinvention; and

FIG. 4 is a flow diagram showing the scanning method for saving somecompensation memory according to one preferred embodiment of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1 is a block diagram showing a scanning device capable of savingcompensation memory according to one preferred embodiment of thisinvention. As shown in FIG. 1, the scanning device includes an inputdevice 10, an application-specific integrated circuit 16, a compensationmemory unit 18, an image memory unit 20 and an input/output interface22. The input device 10 further includes a sensing device 12 and ananalog/digital converter 14.

The sensing device 12 couples with the analog/digital converter 14. Theanalog/digital converter 14 couples with the application-specificintegrated circuit 16. The compensation memory unit 18, the image memoryunit 20 and the input/output interface 22 all couple with theapplication-specific integrated circuit 16.

FIG. 2 is a schematic diagram of an alternative-sensing device forholding compensation data according to one preferred embodiment of thisinvention. In this embodiment, the alternative-sensing device of FIG. 2may be used as the sensing device 12 of FIG. 1. Before the scanningdevice scans an image object, a compensation procedure is performed. Ingeneral, white is used as a compensation color. When the scanning deviceis conducting a compensation procedure, CCD cells 1×.about.N× (FIG. 2)of the sensing device 12 of FIG. 1 will convert the sensed lightintensity into respective currents and transfer to the storageelectrodes for producing signal charges. The charges are thentransformed to appropriate voltage differential. The alternative-sensingdevice uses such procedure to perform an alternate scanning of thecompensation white so that a multiple of alternative scanning pixels areoutput to the analog/digital converter 14 of FIG. 1. In addition, alinear sensing device similar to the one shown in FIG. 3 may also beused as the sensing device 12 of FIG. 1.

As the analog/digital converter 14 of FIG. 1 receives the alternatelyscanned image pixels, alternate scanned pixels in an analog format aredigitized into even data values and odd data values. Thereafter, theeven data values and the odd data values are transferred to theapplication-specific integrated circuit 16 of FIG. 1.

The application-specific integrated circuit 16 of FIG. 1 receives theeven data values and the odd data values. After performing a computationusing the even data values, the odd data values and preset values, theapplication-specific integrated circuit 16 of FIG. 1 averages out theeven compensation values and the odd compensation values to produceaveraged odd-even compensation values. The averaged odd-evencompensation values are stored inside the compensation memory unit 18 ofFIG. 1. For example, when one of the even 2×CCD cells and one of the odd1×CCD cells scan an image pixel, optical data are converted into an evendata value=250 and an odd data value=262 via the analog/digitalconverter. The application-specific integrated circuit 16 of FIG. 1receives both the even data value and the odd data value. Inside theapplication-specific integrated circuit 16 of FIG. 1, a preset value=255is subtracted from the even value data=250 to produce an evencompensation value=−5. Similarly, a preset value=255 is subtracted fromthe odd value data=262 to produce an odd compensation value=7.Thereafter, the even compensation value and the odd compensation valueare averaged ((even compensation value=−5+odd compensation value=7)/2)to produce an averaged odd-even compensation value=1. Finally, theaveraged odd-even compensation value is transferred to the compensationmemory unit 18 of FIG. 1. In this embodiment, compensation white is usedas color compensation. Hence, the preset value is 255.

After performing the compensation procedure, the scanning device startsto scan an object document. The even 2×CCD cells and the odd 1×CCD cellsscan image pixels and the optical data are converted into even datavalues and odd data values by the analog/digital converter 14 of FIG. 1.The resultant data values are transferred to the application-specificintegrated circuit 16 of FIG. 1. At this stage, the averaged odd-evencompensation value=1 is retrieved from the compensation memory unit 18of FIG. 1. After adding the averaged odd-even compensation value to theeven data value and the odd data value, a pair of image values is outputto the image memory unit 20 of FIG. 1. The odd and even image valuesreside in the image memory unit 20 of FIG. 1 until they are required bythe input/output interface 22 of FIG. 1. When such moment arrives, theapplication-specific integrated circuit 16 of FIG. 1 reads out the pairof image values from the image memory unit 20 of FIG. 1 and sends themto the input/output interface 22 of FIG. 1.

According to the flow described in FIG. 1, a flow diagram showing thescanning method for saving some compensation memory is produced in FIG.4. As shown in FIG. 4, step S400 is executed to provide an evencompensation value and an odd compensation value. Step S402 is executedto average out the even compensation value and the odd compensationvalue and produce an averaged odd-even compensation value. Finally, stepS404 is executed using the averaged odd-even compensation value tocompensate for the values obtained from even pixel position and oddpixel position during a scanning operation.

In this invention, compensation values are split up into oddcompensation values and even compensation values. The odd and evencompensation values are then averaged to produce an averaged odd-evencompensation value. Since a pair of CCD cells uses the same odd-evencompensation value after each scanning operation, memory capacityrequired for compensation data storage is cut in half.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. An application-specific integrated circuit having stored thereoninstructions that, when executed, result in: receiving an even datavalue obtained from an even-numbered pixel of a scanner and an odd datavalue obtained from an odd-numbered pixel of the scanner; performing acomputation using the even data value, the odd data value, and a presetvalue to produce an even compensation value and an odd compensationvalue; and averaging the even compensation value and the oddcompensation value to produce an averaged odd-even compensation value.2. The application-specific integrated circuit of claim 1, wherein theaveraged odd-even compensation value is further produced substantiallyby a process, comprising: employing an alternative-sensing device toperform a plurality of alternate scanning operations on a document andsequentially obtain a plurality of alternatively scanned pixels; andemploying an analog/digital converter coupled to the alternative-sensingdevice to digitize the alternately scanned pixel data in analog formatinto even data values and odd data values.
 3. The application-specificintegrated circuit of claim 1, wherein the averaged odd-evencompensation value is further produced substantially by a process,comprising: employing a linear sensing device to perform a plurality oflinear scanning operations on a document and sequentially obtain aplurality of linearly scanning pixels; and employing an analog/digitalconverter coupled to the linear sensing device to digitize the linearlyscanned pixel data in analog format into even data values and odd datavalues.
 4. An apparatus, comprising: means for receiving an evencompensation value for compensating an even-numbered pixel and an oddcompensation value for compensating an odd-numbered pixel; means forgenerating an odd-even compensation value based, at least in part, onthe even compensation value and the odd compensation value; and meansfor compensating an even-numbered pixel value and an odd-numbered pixelvalue by employing the odd-even compensation value.
 5. The apparatus ofclaim 4, further comprising: means for obtaining values associated witha plurality of alternately scanned pixels; and means for digitizing thealternately scanned pixel values into even data values and odd datavalues.
 6. The apparatus of claim 4, further comprising: means forcombining the odd-even compensation value with the even-numbered pixelvalue and the odd-numbered pixel value.
 7. An article comprising astorage medium having stored thereon instructions that, when executed,result in: performing a computation using an even data value obtainedfrom an even-numbered pixel of a scanning device, an odd data valueobtained from an odd-numbered pixel of the scanning device, and a presetvalue to produce an even compensation value and an odd compensationvalue; generating an odd-even compensation value based, at least inpart, on the even compensation value and the odd compensation value; andcompensating an even-numbered pixel value and an odd-numbered pixelvalue of the scanning device by using the odd-even compensation value.8. The article of claim 7, wherein the instructions, when executed,further result in: performing a plurality of alternate scanningoperations on a document to sequentially obtain a plurality ofalternately scanned pixels; and digitizing the alternately scanned pixeldata in analog format respectively into even data values and odd datavalues.
 9. The article of claim 7, wherein said generating the saidodd-even compensation value further comprises generating the odd-evencompensation value based, at least in part, on an average of the evencompensation value and the odd compensation value.
 10. Acomputer-readable medium having instructions stored thereon, whereinwhen the instructions are executed by a processing device, theinstructions are operable to: receive an even compensation value forcompensating an even-numbered pixel and an odd compensation value forcompensating an odd-numbered pixel; generate an odd-even compensationvalue based, at least in part, on the even compensation value and theodd compensation value; and use the odd-even compensation value tocompensate an even-numbered pixel value and an odd-numbered pixel valueobtained from a scanner.
 11. The computer-readable medium of claim 10,wherein the instructions are further operable to: obtain values from thescanner corresponding to a plurality of alternately scanned pixels; anddigitize the alternately scanned pixel values respectively into evendata values and odd data values.
 12. The computer-readable medium ofclaim 10, wherein the instructions are further operable to: compensatethe even-numbered pixel value and the odd-numbered pixel value by addinga corresponding odd-even compensation value to the even-numbered pixelvalue and the odd-numbered pixel value.
 13. The computer-readable mediumof claim 10, wherein the odd-even compensation value is generated based,at least in part, on an average of the even compensation value and theodd compensation value.
 14. A method, comprising: receiving a shadingvalue obtained from a compensation procedure for an even-numbered pixeland an odd-numbered pixel of a scanner; producing an odd-even shadingcompensation value by use of the even-numbered pixel shading value andthe odd-numbered pixel shading value; and performing shadingcompensation for an even-numbered pixel value and an odd-numbered pixelvalue obtained from the scanner based, at least in part, on the odd-evenshading compensation value.
 15. The method of claim 14, furthercomprising: obtaining values from the scanner associated with aplurality of alternately scanned pixels; and digitizing the alternatelyscanned pixel values into even data values and odd data values.